1. Field of the Invention
This invention relates to an apparatus and method for producing bar flats by a rolled process for improved productivity and economy as well as with improved edge and surface properties.
2. Description of the Related Art
A bar flat is a strip of metal of a predetermined length and thickness. The top and bottom portions of the bar flat as well as the edges have a smooth finish. In a number of industries, bar flats of various thicknesses and widths are employed in the fabrication of products in which a smooth surface finish and. dimensional accuracy of the bar is essential. It is known that a bar flat having a smooth surface can be produced by drawing material through a carbide die.
A cold finished bar flat is defined as a bar having cold work surfaces for an improved bright smooth surface finish and having a predetermined width and thickness tolerances as defined under ASTM standards A108 and A29.
U.S. Pat. No. 3,875,785 describes a die for reducing and sizing rolled sections of various shapes from aluminum, steel, titanium and other alloys to form a cold reduced bar flat. Upper and lower plates move towards each other and the rolled section is drawn through the die. After leaving the die, the lateral sides of the section are trimmed by a pair of knives to the dimensions of a finished article. The use of a die has the shortcoming that internal stresses are formed in the articles of manufacture by the drawing action of the die. Prior art drawn methods have the additional shortcoming of requiring complicated machinery which results in high manufacturing costs.
Another practice for forming metal strips of a desired width is to cut the strip from a larger metal sheet. Metal strips obtained in this manner have burrs and sharp edges which are undesirable. U.S. Pat. No. 3,724,251 describes an apparatus for edge conditioning strips cut from a metal sheet. The metal sheet is passed through a slitter for severing the sheet into strips of a desired width. A number of pairs of opposing rollers are disposed adjacent the edges of the strip. Sharp corners and burrs are rolled from the edges of the strip. However, this patent has the shortcoming that dimension accuracy of the bar flat to cold finished standards would not be obtained by this method.
U.S. Pat. No. 3,768,293 describes an apparatus for conditioning the edges of metal strip material. Material is delivered from a web slitting apparatus to edge conditioning rollers. The edge conditioning rollers are grooved rollers arranged in pairs along the edges of the strip. The strip is drawn through cutter blades for cutting formations into the strips. Edge finishing rollers apply pressure to round and smooth the cut edges.
Of possible general relevance are U.S. Pat. Nos. 3,254,568 and 3,416,347 directed to edge conditioning of metal strips.
It is desirable to provide an apparatus for providing a combination of cold rolling and edge conditioning to produce desired smoothness and dimensional accuracy of cold finished bar flats by the rolled method without undue internal stress to the bar. It is also desirable to provide a cold finished bar flat with a bright smooth surface finish which is easily manufactured by the rolled method with improved productivity and economy.